Catalytic muffler



June 18, 1963 w. B. INNES ETAL CATALYTIC MUFFLER Filed July 22, 1960 INV EN TORS W ILL/AM B. lN/VES WA L 7'5 M ORDACH ATTORNEY United StatesPatent @fiice 3,094,394 Patented June 18, 1963 3,0?4,394 CATALYTICMUFFLER William B. Innes and Walter Mordach, Stamford, Conn, assignorsto American Cyanamid Company, New York, N.Y., a corporation of MaineFiled July 22, 1960, Ser. No. 44,674 3 Claims. (C1. 23-28S) Thisinvention relates to catalytic apparatus of the type employable with aninternal combustion engine for oxidizing the toxic and obnoxiouscomponents of hydrocarbon combustion exhaust gases.

More particularly, the present invention relates to a catalyticconverter and more preferably, a catalytic converter which is capable ofbeing readily inserted into the exhaust system of an internal combustionengine as, for example, in lieu of a muflier therein. Suitableconverters may be inserted before or after the exhaust manifold or otherconvenient locations.

The exhaust gases from the combustion of hydrocarbon fuels such asgasoline, diesel fuel and the like in internal combustion engines,contain mixtures of carbon monoxide and various hydrocarbons, bothsaturated and unsatu rated, nitrogen and other constituents. Thesemixtures are both poisonous and obnoxious.

In addition to the known hazards resulting from the inhalation ofcombustion exhaust gases of hydrocarbon fuels, such gases have, ofcomparatively recent times, been identified with smog formation and, toa lesser extent, with various forms of cancer.

Thus, it is known that exhaust gases from automobiles, particularlyolefin and nitrogen oxide components, have been demonstrated to be aprimary cause of photochemical smog in heavily populated metropolitancenters of this country, such as Los Angeles, California. Smog, as theterm is generally employed, is broadly understood to refer to a varietyof phenomena which are related to the interaction of nitrogen oxides,hydrocarbons and sunlight. These include a fog-like haze, high oxidantconcentration in the atmosphere (mostly ozone), eye irritation, plantdamage and the like. In general, smog is defined more fully in anarticle by W. L. Faith, entitled Nature of Smog, in Chemical EngineeringProgress, 53, 406 (1957).

The hazards and nuisance created by hydrocarbon combustion exhaust gasesfrom internal combustion engines have, over the years, resulted in anumber of processes, catalysts and apparatus whereby the reduction orthe elimination of the harmful components of these gases has been theprimary object.

A relatively common device employed for this purpose has been what issometimes referred to as a catalytic mufller which normally refers to adevice which is to be substituted into the exhaust line of an internalcombustion engine in lieu of a mufiler. This has been a particularlypreferred area of activity in View of the fact that the cost of such adevice is reduced by the cost of a conventional muffler normallyemployed, and by other obvious advantages. Such devices are insertedinto the exhaust line of an internal combustion engine and by the actionof catalysts contained therein, oxidize the exhaust gases so that theexit gases from the muflier contain reduced amounts of the harmful andobnoxious constituents of the exhaust gases.

To our knowledge, none of these devices have in the past provedsuccessful, probably because of a number of practical considerations.Among these might be included the development of significant backpressures, the size, weight and cost of such devices, the comparativeshort activity life of catalysts employed and the difiiculty ofrecharging the device with fresh catalysts, the inability of many ofthese devices to withstand the elevated temperatures obtained in thecatalytic oxidation of exhaust gases, the difiiculty in achievinguniform conditions in such devices under operating conditions and thedifficulty in maintaining the catalyst bed under a constant pressure soas to prevent the formation of voids therein whereby the catalyst israpidly and prematurely attrited and whereby catalyst is prematurelydeactivated through the development of hot spots in the catalyst bed.

The present invention has for its principal object the providing of acatalytic converter and, more preferably, a catalytic mufller wherebyuniform conditions are maintained both in the operation of the internalcombustion engine and in the muffler itself by virtue of its noveldesign.

It is a particular object of the present invention to provide such acatalytic muffler which is of simple construction, is easily adaptableto be positioned in the exhaust line of an internal combustion engineand may be readily recharged after deactivation of the catalystcontained therein.

It is a further and particular object of the present invention toprovide a catalytic muffler so constructed that losses in catalysts dueto attrition are readily and automatically compensated for and wherebythe presence of voids otherwise formed in a catalyst bed areautomatically eliminated, thus avoiding excessive attrition anddeactivation.

It is a further and particular object of this invention to provide acatalytic muffler which, in the event that excessively high temperaturesare achieved during its normal operation, automatic means for permittingthe ready exit of the unoxidized exhaust gases is provided.

Further objects include providing a catalytic muffler whichsubstantially eliminates pressure drop or results in a low pressure dropdue to minimum back pressure, and to provide a muffler device whicheffects good noise elimination.

These and other objects, advantages and features of the presentinvention will become more'apparent from the detailed descriptionthereof set forth, which description is particularly in reference to theaccompanying drawing of which:

' FIGURE 1 is a longitudinal cross-sectional view of the catalyticconverter contemplated by this invention;

FIGURE 2 is a sectional view along the line 22 of FIGURE 1; and

' FIGURE 3 is an end view of the converter of FIG- URE 1.

In accordance with the present invention, a catalytic converter isprovided comprising a cylindrical housing having an inlet end and anoutlet end, and having centrally positioned therein a longitudinallyextending cylindrical tube, which is perforated intermediate its ends. Alongitudinally extending perforated cylindrical sleeve having across-section greater than that of the aforesaid cylindrical tube butless than that of said housing is positioned intermediate the inlet andoutlet ends of the cylindrical housing and the area between the saidcylindrical sleeve and tube define the bed for hydrocarbon combustionexhaust catalyst. The area between the outside surface of said sleeveand said inside surface of said housing define a space for catalyticallyoxidized exhaust gases to be carried to the outlet end of the housing.The catalytic mufiier of this invention is of a symmetrical designwhereby uniform operating conditions are maintained for both theinternal combustion exhaust engine and in the catalytic muflier itself.

While caflalytic mufflers of this invention are described as beingcylindrical and as being of symmetrical design, it should be noted thatthe term cylindrical as employed herein also contemplates catalyticconverters having elipa tical configurations. In all of the convertersof this invention the construction may further be described as beingradial in that the catalyst bed extends outwardly from the center of thedevice where the exhaust gases enter. It is essentially this radialarrangement from which uniform operation conditions, faster warm uptimes, and maximum flexibility of construction are accomplished thatcomprise the essential elements of this invention.

At the inlet end of the catalytic muffler, means are provided for theaddition of air to the combustion exhaust gases entering the catalyticmulfler. This may be accomplished by the construction of a venturi atthe inlet end thereby avoiding the need for pumps and other complicatedand expensive devices readily subject to mechanical failure.

Further, at the inlet end of the device, inside the cylindrical housingand surrounding the centrally disposed cylindrical tube through whichthe exhaust gases enter the catalytic chamber, a catalyst reservoir isprovided which may contain, for example, between 2 and percent or moreof the total volume of catalysts in the activity zone. Means areprovided for maintaining a uniform and steady pressure on this catalystreservoir as, for example, a spring which means preferably have anexternal or exposed element whereby pressure on the reservoir may beperio dically increased as the catalyst attrits. This aspect of thepresent invention is particularly desirable in that it permits, a user,by comparatively simple adjustment, to maintain the catalyst bed in thiscatalytic mufiler of uniform density and thereby prevents excessiveattrition and premature deactivation of the catalyst.

At the exit end of the catalytic muffler, means areprovided for closingthe catalyst bed as for example, a suitable plate-like member disposedabout the central tube. In order to recharge the muffler, thisplate-like member must be removed and so it may be connected to theoutside end plate that this may be accomplished readily. Alternatively,such a plate-like member may be placed under pressure as for example bymeans of springs.

A further important aspect of this invention involves the employment ofrelief means whereby when the catalyst bed reaches a predetermined andundesirable intense heat, which if allowed to continue would result inthe ready deactivation and possible destruction of the catalystcontained therein as well as the container; a cap or other closing meanspositioned at the exit end of the centrally positioned cylindrical tubeis released, permitting the combustion exhaust gases to flow directlythrough the device without benefit of contact and oxidation by thecatalyst bed. Such a means could involve a heat sensitive cap subject tomelting at a predetermined temperature or, and preferably, a cappingmeans maintained in the closed position by a heat fusible element whichwhen a predetermined heat is reached becomes molten enabling the cappingmeans to be opened merely by the force of unoxidized exhaust gasescontacting the same.

Referring to the drawing, in which a specific illustrative embodiment ofthis invention will be described, it will be seen that a catalyticmuffler A of a cylindrical configuration and a symmetrical design isshown comprising a cylindrical housing 1, preferably of a high gradeheat resistant steel, though in general steels or metals, and preferablylight weight metals able to resist temperatures of up to 750 C. may beemployed. Said cylindrical housing 1 has an inlet end plate 2 and anoutlet end plate 3 and having extending at right angles from end plates2 and 3 centrally positioned inlet and outlet tubes 4 and 5respectively. Tubes 4 and 5, in general, provide a convenient means foradapting the catalytic muffler of this invention into an exhaust systemof an internal combustion engine and for purposes of this descriptionare of substantially the same diameter. With respect to tube 4, it willbe noted that this tube extends into the housing 1 in a centrallydisposed longitudinal plane terminating a short distance from the insidesurface 6 of exit end 3 and in the same plane as exit tube 5. Thisportion of tube 4 is comprised 'of a major perforated segment 7 whichsegment may be said to comprise a major and central portion of theinternal segment of tube 4.

The entrance end of tube 4 is designed in the form of a venturi wherebythe combustion exhaust gases are readily mixed with air or otheroxidizing gas to insure their complete oxidation. The venturi iscomposed of a centrally disposed tapered cone 8, the narrowed inner end9 of which is positioned between but spaced from the inside walls of acollar-like member 10, the end of which extends inward from narrowed end9 but is spaced from the perforation 7 in the central portion of tube 4.An opening 1 1 in the upper surface of the external portion of tube 4 isthe entrance for air which is drawn in by the raw combustion exhaustgases entering the external end of tube 4 from the exhaust line of theinternal combustion engine.

Positioned about the longitudinally extending cylindrical tube 4 is alongitudinally extending perforated heat resistant metal sleeve 12having a crosssection greater than that of said cylindrical tube 4 butless than that of the inside diameter of housing 1. In general, thediameter of sleeve 12 will be from about 1.5 to about 3 times thediameter of tube 4. In this illustrative embodiment it is about 2.5times. The cylindrical sleeve 12 has perforations l3 and is of a lengthsubstantially equal to the length of the internally disposed portiontube 4. Sleeve 12 may be welded to the inside surface of inlet entranceplate 2 or otherwise supported therein by suitably positioned lugs orthe like. Positioned between the outer surface of longitudinallyextending tube 4- and longitudinally extending sleeve 12 is the catalystbed 14 containing a suitable oxidizing catalyst 15. Such catalysts maybe any of a number suitable for use for this purpose as, for example, aniron oxide-chromium oxide catalyst prepared from to 97 percent of E2 0and 0.5 to about 15 percent of Cr O which is described in copendingapplication Serial No. 786,973, filed January 15, 1959. Alternatively,such catalysts may be of the type described in U.S. Patent 2,912,300.

Exit pipe is preferably joined to end plate 3 as by a weld or othersuitable means. Extending perpendicular from the inside surface 6 ofplate 3 are arms 16 which in turn are connected to a circular plate 17having a centrally disposed opening therein for receiving the exit endof longitudinally positioned tube 4. When assem bled, as will be seen inFIGURE 1, plate 17, positioned on arms 16, functions as a retainingmember for the catalyst 15 in catalyst bed 14. Alternatively, springs 18(only one of which is shown only on a lower arm 16) may be positionedover the arms 16, as a means of maintaining a force at the exit end ofthe mufiier to maintain the density of the catalyst bed. In such anarrangement it will be apparent that plate 17 is free for longitudinalmovement.

The exit end plate 3 is mechanically joined to the cylindrical housing 1in that the exit end of said housing contains an annular flange 19, saidannular flange I9 and exit plate 3 having correspondingly positionedholes 25 in their peripheral edges for receiving a suitable number ofbolts 21 which are secured in position by nuts 22. It will be seen thatsuch an arrangement provides an easy method for removing deactivatedcatalyst from catalyst bed 14 and permits the ready and rapid refillingof said catalyst bed.

At the inlet end of the illustrative exhaust muffler, the catalyst bedis provided with a reservoir area 23 which may, depending upon theparticular device, contain from between about 2 and about 10 percent ormore of the total catalyst charged to a given catalyst bed. In eifect,this reservoir area 23, which area can be varied by the amount ofcompression placed on springs 24 normally does not include catalystparticles extending over the perforated portion of tube 4. Reservoirarea 23 has positioned at its outside end a ring-like plate 25 which hasa centrally disposed opening for receiving tube 4. Plate 25 is movablypositioned between the outside surface of tube 4 and the inside surfaceof sleeve f2. Positioned between outside surface of plate 25 and theinside surface of the entrance end plate 2 is a second cylindrical plate26 having a centrally disposed opening which also is free forlongitudinal movement and positioned between said plate 26 and saidplate 25 are a plurality of coil springs 24. Preferably, springs 24 aremade of a highly heat resistant steel alloy and is preferably positionedin a refractory wool or other stabilized heat resisting media 25a.

Extending through thread retaining nuts 27 positioned in contact withinlet end plate 2 are a plurality of screws 28. The inside end of screws28 are in contact with the outside surface of plate 26 and as will beapparent by turning the screw in the appropriate direction, the pressure of springs 24 can be brought to bear on plate 25 and consequentlythe catalyst reservoir in the reservoir area. Such an arrangementenables the user to maintain a uniform density in the catalyst bedsimply by tightening screw 28. In this connection it will be noted thata fully packed uniform density is important if excessive losses due toattrition is to be avoided. In addition, the action of the springs alonewill compensate for some loss in bed density due to attrition.

The outlet or exit end of centrally disposed tube 4 has thereon a cap 29which is connected to a wire 30 extending through the upper surface oftube 4 through the catalyst bed 14 and is looped 31 between the internalsurface of cylindrical housing 1 and the outer surface of sleeve 12.Positioned about the loop 31 is a heat sensitive metallic ring 32. Wire30 then extends through the upper surface of cylindrical housing 1 whereit is coiled 33 and the end thereof afiixed to a mounting stud 34. Thissimple device insures that the catalyst bed will not be prematurelydeactivated and the device overheated as, for example, as a result ofthe misfiring of a cylinder in an internal combustion engine, in that asthe temperature of the oxidized combustion exhaust gases exceed apredetermined temperature as, for example, 800 C., loop 31 flowspermitting the coiled 33 and loop 31 portion of the wire to be stretchedunder the force of the combustion exhaust gases against the insidesurface of cap 29. This permits the direct exit of the raw exhaust gasesthrough outlet pipe 5, whereby little or no oxidation is effected.

As will be apparent in the operation of the instant device, thehydrocarbon combustion exaust gases enter inlet pipe 4 and the force oftheir movement results in air entering the venturi arrangement at theentrance end through opening it. This mixture then enters the centralperforated portion of tube 4 from Where it is distributed readily to thecatalyst bed 12 through perforations 7 Where it is oxidized and entersinto the conduit or channel-like area between the inside surface ofhousing 1 and the outside surface of sleeve 12 through perforations 13.The natural direction of flow is then to the outlet end of the deviceand the ultimate emission of the oxidizing gases through outlet pipe 5directly into the atmosphere or into suitable conduit for emission intothe atmosphere The employment of a device of the type illustrated inFIGURES 1-3 whereby the inlet gas enters at the center of thecylindrical mufiler device in addition to being capable of simpleadaptation to the above described and illustrative combinations (meansfor maintaining catalyst bed density etc.) its construction lessensWarm-up time significantly in that the maximum amount of exhaust gascontacts the maximum amount of catalyst in the briefest time period.Thus mufflers of the type of this invention are in general characterizedby more rapid warm-up than units with a centrally positioned catalystbed, such as is described in US. Patent 2,909,415.

It will be evident from the present description that the catalyticniufiler device of this invention results in low catalytic attrition andfast warm-up in addition to being of easy and simple assembly andmanufacture. It will be apparent that other numerous modifications andadvantages of this invention will be obvious and, therefore, nolimitations should be set thereon except insofar as they are set forthin the appended claims.

We claim:

1. A catalytic muffler for oxidizing hydrocarbon combustion exhaustgases comprising a cylindrical housing having an inlet end and an outletend, a longitudinally extending cylindrical tube centrally positionedwithin said housing between said inlet end and said outlet end andextending from said inlet end, that portion of said tube within saidhousing being perforated, a capping element for said tube adjacent saidoutlet end, a longitudinally extending perforated cylindrical sleeveWithin said housing and surrounding said tube, said sleeve having acrosssection greater than that of said tube but less than that of saidhousing, catalyst particles for oxidizing said hydrocarbon combustionexhaust gases disposed within the zone defined by said tube and saidsleeve, a plate like retaining member transversely situated between saidtube and said sleeve adjacent to said outlet end of said housing, thearea between the outer surface of said sleeve and the inner surface ofsaid housing defining a zone for catalytically oxidized exhaust gases tobe carried to the outlet end of said housing, a moveable disk positionedwithin said housing and adjacent to the inlet end of said housing saiddisk being slideably fitted for longitudinal movement over said tube,the inner surface of said disk disposed to be in contact with catalystparticles in said catalyst zone and yieldable means contacting saidslideably mounted disk whereby a force is created by said means againstsaid catalyst particles so as to maintain said zone free of voids.

2. A catalytic muffler according to claim 1 in which a venturi ispositioned Within said tube and adjacent said inlet end, that portion ofsaid tube extending from said inlet end of said housing having anorifice for admitting air under the influence of the moving hydrocarboncombustion exhaust gases to be oxidized.

3. A catalytic mufiler according to claim 1 having means for retainingsaid capping element in a normally closed position and a heat sensitiveelement secured to said retaining means whereby when said heat sensitiveelement reaches a predetermined temperature, said retaining means isreleased thus permitting said capping element to open from a normallyclosed position thereby allowing hydrocarbon combustion exhaust gases topass from said outlet end of said housing without significant oxidation.

References Cited in the file of this patent UNITED STATES PATENTS1,465,904 'Herdle Aug. 21, 1923 1,605,484 Thompson et al. Nov. 2, 19261,794,276 Bowes Feb. 24, 1931 2,071,119 Harger Feb. 16, 1937 2,260,578Murray Oct. 28, 1941 2,378,083 Hull June 12, 1945 2,937,490 Calvert May24, 1960 2,956,865 Williams Oct. 18, 1960

1. A CATALYTIC MUFFLER FOR OXIDIZING HYDROCARBON COMBUSTION EXHAUSTGASES COMPRISING A CYLINDRICAL HOUSING HAVING AN INLET END AND AN OUTLETEND, A LONGITUDINALLY EXTENDING CYLINDRICAL TUBE CENTRALLY POSITIONEDWITHIN SAID HOUSING BETWEEN SAID INLET END AND SAID OUTLET END ANDEXTENDING FROM SAID INLET END, THAT PORTION OF SAID TUBE WITHIN SAIDHOUSING BEING PERFORATED, A CAPPING ELEMENT FOR SAID TUBE ADJACENT SAIDOUTLET END, A LONGITUDINALLY EXTENDING PERFORATED CYLINDRICAL SLEEVEWITHIN SAID HOUSING AND SURROUNDING SAID TUBE, SAID SLEEVE HAVING ACROSSSECTION GREATER THAN THAT OF SAID TUBE BUT LESS THAN THAT OF SAIDHOUSING, CATALYST PARTICLES FOR OXIDIZING SAID HYDROCARBON COMBUSTIONEXHAUST GASES DISPOSED WITHIN THE ZONE DEFINED BY SAID TUBE AND SAIDSLEEVE, A PLATE LIKE RETAINING MEMBER TRANSVERSELY SITUATED BETWEEN SAIDTUBE AND SAID SLEEVE ADJACENT TO SAID OUTLET END OF SAID HOUSING, THEAREA BETWEEN THE OUTER SURFACE OF SAID SLEEVE AND THE INNER SURFACE OFSAID HOUSNG DEFINING A ZONE FOR CATALYTICALLY OXIDIZED EXHAUST GASES TOBE CARRIED TO THE OUTLET END OF SAID HOUSING, A MOVEABLE DISK POSITIONEDWITHIN SAID HOUSING AND ADJACENT TO THE INLET END OF SAID HOUSING SAIDDISK BEING SLIDEABLY FITTED FOR LONGITUDINAL MOVEMENT OVER SAID TUBE,AND INNER SURFACE OF SAID DISK DISPOSED TO BE IN CONTACT WITH CATALYSTPARTICLES IN SAID CATALYST ZONE AND YIELDABLE MEANS CONTACTING SAIDSLIDEABLY MOUNTED DISK WHEREBY A FORCE IS CREATED BY SAID MEANS AGAINSTSAID CATALYST PARTICLES SO AS TO MAINTAIN SAID ZONE FREE OF VOIDS.